The subject matter disclosed herein generally relates to propellers and propeller-driven aircraft. More specifically, the subject disclosure relates to propeller blade pitch control.
Propellers producing thrust or pressure in a non-uniform flow field are subject to sinusoidal variation of the thrust load on the propeller blades, known in the propeller science as a 1 P (once per revolution) load. This phenomenon occurs, for example, when the propeller is subjected to an angular inflow, an inflow that is non-parallel to the propeller shaft. Such angular inflow is common when an aircraft is in a yaw or G-producing maneuver such as a turn or a climb at takeoff
The 1 P load manifests itself as a moment on the propeller shaft that lags the inflow angle by 90 degrees as a result of the advancing blade seeing a higher angle of attack and the receding blade seeing a lower angle of attack. This load must be reacted by the aircraft structure and is countered by various control surfaces on the aircraft, resulting in additional structural weight to react the load and larger control surfaces, and associated aircraft drag, to counter the moment. The art would well receive a way to reduce the 1 P load which would, in turn, result in an aircraft weight savings and reduction in reduction in control surface size necessary to counter the load.